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This simulation is designed to help learners visualize atomic structure, as they drag protons, neutrons, and electrons to construct an atom. As particles are moved into place in the nucleus or the electron orbits, the simulation automatically displays the net charge, mass number, atomic symbol, and name of the element. After practicing with atom-building, users can test their skills against the clock in a game with four levels of increasing difficulty. See Related Materials for a lesson plan and student guide developed by the PhET project specifically for use with Build An Atom.

This lesson is part of PhET (Physics Education Technology Project), a large collection of free interactive simulations for science education.

Please note that this resource requires
Java Applet Plug-in.

Editor's Note:This particular atom-building simulation is pedagogically appropriate for adolescent learners with little or no background in physics. It has built-in scaffolds that promote deeper understanding of the atom, while also building a foundation for teaching about isotopes and ions. It can be adapted for students at all ability levels, grades 6-12.

Standards (28)

AAAS Benchmark Alignments (2008 Version)

4. The Physical Setting

6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.

6-8: 4D/M1b. The atoms of any element are like other atoms of the same element, but are different from the atoms of other elements.

9-12: 4D/H1. Atoms are made of a positively charged nucleus surrounded by negatively charged electrons. The nucleus is a tiny fraction of the volume of an atom but makes up almost all of its mass. The nucleus is composed of protons and neutrons which have roughly the same mass but differ in that protons are positively charged while neutrons have no electric charge.

9-12: 4D/H2. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.

9-12: 4D/H5. Scientists continue to investigate atoms and have discovered even smaller constituents of which neutrons and protons are made.

4G. Forces of Nature

9-12: 4G/H3. Most materials have equal numbers of protons and electrons and are therefore electrically neutral. In most cases, a material acquires a negative charge by gaining electrons and acquires a positive charge by losing electrons. Even a tiny imbalance in the number of protons and electrons in an object can produce noticeable electric forces on other objects.

9-12: 4G/H8. The motion of electrons is far more affected by electrical forces than protons are because electrons are much less massive and are outside of the nucleus.

11. Common Themes

11B. Models

6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.

6-8: 11B/M4. Simulations are often useful in modeling events and processes.

11D. Scale

6-8: 11D/M3. Natural phenomena often involve sizes, durations, and speeds that are extremely small or extremely large. These phenomena may be difficult to appreciate because they involve magnitudes far outside human experience.

Matter and Its Interactions (HS-PS1)

Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms. (HS-PS1-1)

Disciplinary Core Ideas (K-12)

Structure and Properties of Matter (PS1.A)

Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it. (6-8)

Each atom has a charged substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons. (9-12)

The periodic table orders elements horizontally by the number of protons in the atom's nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states. (9-12)

The structure and interactions of matter at the bulk scale are determined by electrical forces within and between atoms. (9-12)

Crosscutting Concepts (K-12)

Scale, Proportion, and Quantity (3-12)

Time, space, and energy phenomena can be observed at various scales using models to study systems that are too large or too small. (6-8)

The significance of a phenomenon is dependent on the scale, proportion, and quantity at which it occurs. (9-12)

Structure and Function (K-12)

Complex and microscopic structures and systems can be visualized, modeled, and used to describe how their function depends on the shapes, composition, and relationships among its parts, therefore complex natural structures/systems can be analyzed to determine how they function. (6-8)

Scientific Knowledge Assumes an Order and Consistency in Natural Systems (1-12)

Science assumes the universe is a vast single system in which basic laws are consistent. (9-12)

NGSS Science and Engineering Practices (K-12)

Analyzing and Interpreting Data (K-12)

Analyzing data in 6–8 builds on K–5 and progresses to extending quantitative analysis to investigations, distinguishing between correlation and causation, and basic statistical techniques of data and error analysis. (6-8)

Analyze and interpret data to provide evidence for phenomena. (6-8)

Analyzing data in 9–12 builds on K–8 and progresses to introducing more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data. (9-12)

Analyze data using computational models in order to make valid and reliable scientific claims. (9-12)

Developing and Using Models (K-12)

Modeling in 6–8 builds on K–5 and progresses to developing, using and revising models to describe, test, and predict more abstract phenomena and design systems. (6-8)

Develop a model to describe unobservable mechanisms. (6-8)

Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. (9-12)

Develop a model based on evidence to illustrate the relationships between systems or between components of a system. (9-12)

Use a model to provide mechanistic accounts of phenomena. (9-12)

Using Mathematics and Computational Thinking (5-12)

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. (9-12)

Use mathematical representations of phenomena to describe explanations. (9-12)

Create a computational model or simulation of a phenomenon, designed device, process, or system. (9-12)

NGSS Nature of Science Standards (K-12)

Analyzing and Interpreting Data (K-12)

Analyzing data in 6–8 builds on K–5 and progresses to extending quantitative analysis to investigations, distinguishing between correlation and causation, and basic statistical techniques of data and error analysis. (6-8)

Analyzing data in 9–12 builds on K–8 and progresses to introducing more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data. (9-12)

Developing and Using Models (K-12)

Modeling in 6–8 builds on K–5 and progresses to developing, using and revising models to describe, test, and predict more abstract phenomena and design systems. (6-8)

Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. (9-12)

Using Mathematics and Computational Thinking (5-12)

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. (9-12)

Units (2)

This resource is part of 2 Physics Front Topical Units.

Topic: Particles and Interactions and the Standard ModelUnit Title: Matter and Interactions

Drag protons, neutrons, and electrons to construct your own atom! As particles are moved into the nucleus or the electron orbits, the simulation automatically displays mass number, atomic symbol, name of element, and net charge. After practicing, try your skill against the clock in a game with four levels of difficulty.

Topic: Particles and Interactions and the Standard ModelUnit Title: The Standard Model

Drag protons, neutrons, and electrons to construct your own atom! As particles are moved into the nucleus or the electron orbits, the simulation automatically displays mass number, atomic symbol, name of element, and net charge. After practicing, try your skill against the clock in a game with four levels of difficulty.

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